HAVING clause working in postgres 8.0, but not in 8.2

Hello all,

We have recently upgrade our postgres server from 8.0 to 8.2. I am
experiencing some difficulties in SQL queries.
Let's say I have a table NUMBERS (number (integer)) which has values
1, 5 and 8.

SELECT number FROM numbers; will return 1, 5 and 8.

In PostgreSql 8.0, SELECT number FROM numbers HAVING number = 5;
returns 5

But in 8.2, it gives me the following error: ERROR:  column
"numbers.number" must appear in the GROUP BY clause or be used in an
aggregate function.

In the documentation, it says that HAVING can be used without GROUP BY
or aggregate functions.

Has anybody already experienced this, is this a bug or am I missing
something?

TIA,
Vladimir